For adults: most definitely Typhoon Lagoon
Better theming: lush plants, winding paths, water. Great nostalgic background music.
Good mix of thrill and relaxing attractions. Awesome wave pool, which can be either intense or relaxing, depending how deep you want to go.
If you go in the summer, it will likely rain in the mid-afternoon. With rain comes thunder, which will temporarily close the attractions. Thus both are half-day parks.
Either go at opening (and experience increasing crowds but guaranteed use of the attractions), or monitor the weather and go in the late afternoon (and experience the relatively empty park that happens when they re-open after the thunder passes)